The typical magnitude of diaphragm displacement is 0.1 mm, which is well suited
to a strain-gauge type of displacement-measuring transducer, although other forms of
displacement measurement are also used in some kinds of diaphragm-based sensors. If
the displacement is measured with strain gauges, it is normal to use four strain gauges
arranged in a bridge circuit configuration. The output voltage from the bridge is a
function of the resistance change due to the strain in the diaphragm. This arrangement
automatically provides compensation for environmental temperature changes. Older
pressure transducers of this type used metallic strain gauges bonded to a diaphragm
typically made of stainless steel. However, apart from manufacturing difficulties arising
from the problem of bonding the gauges, metallic strain gauges have a low gauge factor,
which means that the low output from the strain gauge bridge has to be amplified by
an expensive d.c. amplifier. The development of semiconductor (piezoresistive) strain
gauges provided a solution to the low-output problem, as they have gauge factors up